Combination of Resistances

Q.

What is wattless current?

Q.

The given figure shows a battery having an EMF of 9V and internal resistance of $0.6\Omega$, connected to three resistors A, B and C. ?

(a) Calculate the combined resistance of B and C.
(b) Calculate the total resistance of A, B and C.
(c) Calculate the total resistance of the circuit.
(d) Calculate the current in each of the three resistors A, B and C.
[5 MARKS]

Q. In an electrical circuit, three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

1. Brightness of all the bulbs will be the same
2. Brightness of bulb A will be the maximum
3. Brightness of bulb C will be less than that of B
4. Brightness of bulb B will be more than that of A

Q.

What is the maximum current that can be drawn from a cell of emf $E$ and internal resistance $r$ connected to an external resistance $R$?

Q.

Resistors $R_1$=10$\Omega$, $R_2$ = 40$\Omega$, $R_3$ = 30$\Omega$, $R_4$ = 20$\Omega$, $R_5$ = 60$\Omega$ and a 12V battery is connected as shown.

Calculate:
(a) the total resistance
(b) the total current flowing in the circuit. [3 MARKS]

Q.

A current of $ 6A$ enters one corner $ P $of an equilateral triangle $ PQR$ having$ 3 $wires of resistance $ 2\Omega $ each and leaves by the corner$ R$. The currents$ {i}_{1}$ in ampere is______.

Q.

Voltage drop accross 100 ohm resistor is

1. 1 v

2. 10 V

3. 0.1 V

4. 0 V

Q. What is the minimum resistance which can be made using five resistors each of $\frac{1}{5}\Omega$?

1. $\frac{1}{5}\Omega$
2. $\frac{1}{25}\Omega$
3. $\frac{1}{10}\Omega$
4. $25\Omega$

Q.

The p.d. between the terminal of a cell in an open circuit was $2.2V$. When it was measured across a resistor of $5$ it was found to be $1.8V$. The internal resistance of the cell is

1. $\frac{10}{9}\Omega$

2. $\frac{9}{10}\Omega$

3. $\frac{12}{7}$

4. $\frac{7}{12}$

Q.

What are the drawbacks of the meter bridge experiment?

Q.

What number of ohms is a short?

Q. What is a wheat stone bridge ?

Q.

Find the equivalent resistance across the points A and B in the given circuit.

1. 1 $\Omega$

2. 2 $\Omega$

3. 4 $\Omega$

4. 8 $\Omega$

Q. Question 2
An electric lamp of $100\Omega$, a toaster of resistance $50\Omega$, and a water filter of resistance $500\Omega$ are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?

Q.

In the circuit diagram, Find:

(i) total resistance

(ii) current shown by the ammeter A

Q. Three resistors R1= 1 Ω , R2 = 100 Ω , R3 = 1000 Ω are connected in parallel. Which relation holds true?

1. Req. < 1
2. 1 > Req> 100
3. Req = 100
4. 1 > Req > 1000

Q. How will you connect three resistors of $3\Omega$, $4\Omega$ and $7\Omega$ respectively so as to obtain a resultant resistance of $3.5\Omega$?

1. $3\Omega$, $4\Omega$ and $7\Omega$ in series

2. $3\Omega$, $4\Omega$ and $7\Omega$ in parallel.

3. $3\Omega$, and $4\Omega$ in series and then parallel with $7\Omega$.

4. $3\Omega$, and $4\Omega$ in parallel and then series with $7\Omega$.

Q. What is the ammeter reading in the given circuit?

1. $0.4$
2. $1$
3. $0.6$
4. $1.2$

Q. Two electric bulbs marked 25W-220V and 100W-220V are connected in series to a 440V supply. Which of the bulbs will fuse ?

1. Both
2. 100W
3. 25W
4. neither

Q. Question 17
Two resistors of resistance 2 $\Omega$ and 4 $\Omega$ when connected to a battery will have

(a) same current flowing through them when connected in parallel
(b) same current flowing through them when connected in series
(c) same potential difference across them when connected in series
(d) different potential difference across them when connected in parallel

Q.

A voltmeter has low resistance

1. True
2. False

Q.

Four resistors are connected in parallel. Each resistors has a resistance of $2\Omega$. The effective resistance of the combination is:

1. 0.5 Ω

2. 4 Ω

3. 0.25 Ω

4. 8 Ω

Q.
The Figure represents a part of a closed circuit. The potential difference in volts between the points A and B i.e. $V_A-V_B$ is______

Q. A battery of emf $4$ volts and internal resistance $1\Omega$ is connected in parallel with another battery of emf $1$ volt Combination is used to send current through an external resistance $2\Omega$. Calculate current through external resistance and potential difference across external resistance.

Q.

A resistor of 8 Ω is connected in parallel with another resistor R₂. The resultant resistance of the combination is 4 Ω. Then, the value of resistor R₂ is:

1. 12 Ω

2. 4 Ω

3. 8 Ω

4. 16 Ω

Q. Current $I$ in the network shown in figure is

1. $1A$
2. $0.5A$
3. $2A$
4. $5A$

Q.

Given 'n' resistors of resistance R $\Omega$. How should they be connected to get the minimum effective resistance?

1. Parallel

2. Series

3. A combination of series and parallel

4. Can't say

Q. Two cells having the same emf are connected in series through an external resistance $R$. Cells have internal resistances $r_1$ and $r_2$ such that $r_1>r_2$ respectively. When the circuit is closed, the potential difference across the first cell is zero, then the value of $R$ is

1. $(r_1+r_2)$
2. $(r_1-r_2)$
3. $\frac{(r_1-r_2)}{2}$
4. $\frac{(r_1+r_2)}{2}$

Q. The potential difference across an electric heater is 60 V when it draws a current of 4 A from the source. How much current will the heater draw if the potential difference is increased to 120 V.

1. 4 A

2. 8 A

3. 2 A

4. 16 A

Q. A current of 1 A is passed through two resistances 1 $\Omega$ and 2 $\Omega$ connected in parallel. The current flowing through 2 $\Omega$ resistor will be

1. 1 A
2. 3 A
3. 2/3 A
4. 1/3 A